Sputtering means atoms are ejected from a bombarded surface. In a sputter preclean, the surface being cleaned is the wafer. In sputter deposition, a target supplies material that can arrive and remain on the wafer. The word alone does not establish whether the wafer gains or loses material.
Follow the bombarded surface
Ion momentum can displace atoms from a solid surface. The removal contribution is negative for that surface's material balance. A preclean uses this mechanism to remove some surface material before another operation; the target of removal may include an unwanted surface layer. It is not automatically selective only to contamination.
In deposition, atoms ejected from the source travel toward the receiving substrate. Arrival and retention create the added film. The source loses material while the wafer can gain it. Asking only whether a plasma is present misses this distinction.
Process map
A selected 2-step learning trail across courses
Identify wafer-surface material ejection before metal deposition and explain why this is a removal step.
Real step names, layer-by-layer cross-sections, and rationale follow the account access of each target's course.
Net growth can contain a removal contribution
Bias sputter deposition can involve material arrival and wafer resputtering at the same time. The net result depends on the competing contributions. Therefore a deposited layer need not imply that no wafer atoms were ejected, and an operation with energetic ions need not be a net etch.
The seed station provides an added-film example. Its copper supplies a surface for later electrochemical deposition and a current path. It should not be reclassified as a clean simply because PVD and preclean can both involve ion–solid interactions.
Conditions and counterexamples
A preclean that clears an unwanted layer can also alter the desired substrate. A favorable electrical contact after subsequent processing does not independently measure how much each material was removed. Deposition likewise requires evidence of retained material, coverage and the relevant electrical state.
This article distinguishes directions and functions; it does not infer a bombardment setting, source configuration, perfect selectivity or damage-free outcome from a station name.
Trace two material balances
At pre-sputter, name the wafer surface and the material leaving it. At seed deposition, name the incoming film and its downstream purpose. State which surface loses material in each physical operation. The answer should also allow simultaneous incoming and outgoing fluxes without confusing net growth with the absence of sputtering.
References
Silicon VLSI Technology - Full
James D. Plummer, Michael D. Deal, Peter B. Griffin
Silicon VLSI Technology · ISBN 978-0130850379